Vocal communication, through speech, is a fundamental way that humans convey and receive information, and consequently a fundamental function of the auditory system is to encode these vocalizations. How neurons in the auditory system encode vocalizations is unknown, but it is clear that neurons at different levels of the ascending auditory system respond selectively to vocalizations. It has previously been suggested that this selectivity emerges at the level of the inferior colliculus (IC), the main auditory structure in the midbrain. However, selectivity to vocalizations has not previously been examined in the majority of brainstem nuclei, including the cochlear nucleus. Preliminary data in this proposal suggest that neurons in the dorsal cochlear nucleus (DCN) respond selectively to vocalizations, and that they filter specific vocalization-evoked neural responses that help shape selectivity to vocalizations in the IC. The purpose of this project is to test whether neurons in te DCN of awake mice are selective for vocalizations and determine how the circuitry of DCN may shape selectivity to vocalizations at higher levels of the auditory system. The first Aim will use extracellular recordings to test for selectivity to vocalizations in the different cells types in te DCN of awake mice. The second Aim will use deconstructed vocalizations to determine the required elements to evoke responses to vocalizations in DCN and specifically determine whether combinations of high frequency elements in the vocalizations generate distortion products in the cochlea. The third Aim will combine biophysical modeling of DCN neurons and circuitry with extracellular data from Aims 1 and 2 to identify the likely mechanisms responsible for responses to vocalizations. The proposed experiments will provide multiple research and learning experiences for undergraduate students, and enhance the research mission of Washington State University Vancouver, a small, mainly undergraduate campus. The significance will be in advancing understanding of how the ascending auditory system encodes behaviorally relevant sounds. In addition, the auditory brainstem algorithms that result from the proposed integration of electrophysiology and mathematical modeling studies will facilitate development of filtering algorithms that may find applications in signal processing and in development of novel auditory prosthetics.